There are many other factors that can influence a woman's likelihood of getting pregnant, says West, but the main one is age.

"It can take longer the older you are," she says.

According to Professor Geeta Nargund, medical director for Create Fertility, a woman’s "best reproductive years" are in her 20s. When a woman reaches her thirties, her fertility will gradually decline, particularly after the age of 35.

"Each month that she tries, a healthy, fertile 30-year-old woman has a 20% chance of getting pregnant," says Nargund.

Other issues, West adds, include lack of fertility awareness when it comes to sex and understanding ovulation; mindset, which when dealing with uncertainty can be really significant; and lifestyle choices.

In regards to the latter, the effects of alcohol, smoking, drugs and weight are well documented, and there can also be issues with medications such as painkillers and anti-inflammatories, which can also deplete the body of nutrients needed for fertility.

West also flags up that long term use of the contraceptive pill can hide underlying fertility issues.

"Many women nowadays have been on the pill since their teens and don't come off it until their 30s when they decide to have a baby," she explains. "So there may be underlying fertility factors that they aren't aware of."

However, that isn't to say that the pill or any other method of reversible contraception causes infertility, as Halil explains:

"When you stop using contraception your periods and fertility will return to normal, though sometimes ovulation can be delayed or be irregular for a short time after stopping hormonal contraception," she says.

"If you use the contraceptive injection, your periods and fertility may take longer to return to normal than after other methods of contraception."

If after 12 months of having unprotected sex, you haven't conceived then all Halil, West and Nargund agree it's best to contact your GP.

How to boost fertility

For those who want to increase their chances of conceiving, there are a number of tried and tested methods which fertility experts suggest.

Zita West says that women are always looking for that one food that will boost fertility. But it's not that simple.

"Fertility is a whole body event and not just something that happens in the fallopian tubes: you need balanced blood sugar, nutrients for the cell membranes and protection from free radicals.

"Stress, long hours, alcohol: they all deplete you of vital nutrients needed for fertility."

For West, nutrition is the cornerstone of fertility.

"Women know everything about diet but very little about nutrition," she says.

"It's not just about getting pregnant but also about the health of the eggs and sperm, and you can build up the health of the eggs and sperm through diet."

She adds that we need "good fats" for building the cell membranes of sperm and eggs, however trans fats - found in processed foods and microwave meals - can interfere with ovulation.

Vitamin D, iodine and antioxidants - on the other hand - are great.

"When you are trying to conceive, perhaps the saying ‘you are what you eat’ should read ‘you both are what you eat’," says West.

Halil adds that couples who regularly have sex between two and three times a week, will be more likely to conceive, because there will always be sperm waiting to meet the egg at ovulation.

"Some people believe that you need to have sex exactly at the time of ovulation in order to get pregnant," she adds, "but this is not true."

Additionally, there is no evidence that one sexual position is better than any other for getting pregnant.

"As long as your partner ejaculates in your vagina, the sperm will be able to swim to the fallopian tubes," says Halil.

Men should also aim to ejaculate every two to three days in order to keep sperm healthy. It's a "common myth", says Zita West, that a man should save up his sperm.

"Sperm needs to be constantly refreshed for potency, so don’t wait to have sex just when the ovulation kit says so."

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What to do if you're worried you may be infertile

If, after a year of trying for a baby, you still haven't conceived then you need to contact your GP.

Professor Adam Balen, chair of the British Fertility Society, says that couples will be tested for various things by their doctor.

"For the man it’s an infection screening looking for things like chlamydia," he explains.

"Women will have an infection screening too and will also undergo hormonal checks and a blood test to see if they are ovulating."

According to Zita West, you can order a fertility MOT kit in the post, which involves taking a pinprick of blood at home and completing a questionnaire. A nurse will then share the results with you over the phone.

"I would advise couples to attend free open days in fertility or IVF clinics and get more information in order to make informed choices and decisions," adds Professor Nargund, who lists some additional tips for approaching clinics.

:: Always question the scientific evidence - especially if more tests or procedures are advised by clinics, which would increase costs and could lead to more invasive methods.

:: Ask for incidence of complications for women, hospital admissions and success as regards to healthy mother and babies.

:: Do not compare success rates of clinics like a league table as selection of good prognosis patients can increase success rates.

:: Find out about all options available including simple methods and if IVF is required, about Natural, Mild and Conventional IVF.

:: The success of fertility treatment is in helping couples to have a healthy, full-term baby with the least invasive method at the lowest possible cost without putting the woman's health at risk. It is also important to help couples achieve closure if the treatment is not successful.